Hornbostel



Feb. 28, 1956 L, HORNBOSTEL 2,736,247

VANE TYPE STOCK INLET VANE TYPE sToCK INLET Lloyd Hornbostel, Beloit,Wis., assignor to Beloit Iron Works, Beloit, Wis., a corporation ofWisconsin Application December 4, 1951, Serial No. 259,756

6 Claims. (Cl. 9244) This invention relates to an improved stock inletfor a paper machine and, more particularly, to a stock inlet havingimproved ow control means therein.

Transversely extending bafes or walls within the stock inlet boxes areused in the paper making art in an attempt to quiet stock ow through thebox and to prevent the occurrence of eddy currents within the stockilowing therethrough. However, such bailies serve to divide the box intoa plurality of stock compartments, and it is known that dead areas areformed within the sep arate compartments and that stock rolling canoccur within the compartments. The paper stock within such dead areastends to form lumps detrimental to paper quality when later introducedonto the forming wire, while the rolling stock within the separatecompartments interferes with the uniform flow of stock through theinlet, thus aiding in the formation of dead areas.

Various devices which have been substituted for transversely extendingbaies often have been found to reduce the length of stock travel in theinlet box to such an extent that uniform flow across the box cannot beadequately controlled. Ordinarily, the incoming stock is conducted tothe inlet box from a suitable source by means of a pipe substantiallynarrower in width than the inlet box. Stock discharged into the box fromthe pipe tends to iiow heavily through the box from the pipe dischargedirectly to the box discharge or slice gate, and accordingly fails tospread out uniformly during its travel through the box. The problem isadditionally complicated in the case of pressurized inlet boxes, whereinair pressure on the surface of the stock is employed to accelerate theow of stock from the box onto the forming wire, since in suchpressurized stock inlet boxes a high rate of flow of the stock is usedwith a comparatively small overall volume in the stock inlet box.

The present invention provides an improved vane type iiow distributorarrangement within the inlet box, permitting the use of a relativelyshort travel path through the inlet box and also permitting the use, incombination with such a ow distributor arrangement, of rectifier meanssuch as rectifier rolls in certain arrangements so as to obviate thenecessity of employing transversely extending batiies with the attendantoperational di'iculties heretofore encountered.

In general, the stock inlet box of the present invention includes a headbox for a paper making machine provided with means for introducing stockinto the interior of the box and a stock outlet immediately adjacent theforming wire of the paper making machine. At the inlet to the box thereare positioned a plurality of independently adjustable flow directorsadapted to divert stock flow laterally in controllable amounts, therebyto elfect equal or uniform flow in the stock all the way across the headbox. Arrectifier roll or a stack of superimposed rolls extendstransversely across the interior of the inlet behind the flow directormeans for the purpose of replacing the baffle arrangement heretoforeemployed, and preferably a second rectifier roll or group United StatesPatent Ice of rolls is disposed adjacent the box outlet opening toadditionally control the ilow of stock through the opening onto thepaper machine forming wire.

Since the depth of the stock pond in the head box and the air pressureexerted against the stock pond surface are calculated to give a definitevelocity of stock ow in a horizontal path through the box onto theforming wire, the size and number of laterally directed flowdistributors and the number of rectifier rolls in the stack and the sizeof the rolls will be determined by the Velocity desired for stock flow.Preferably, the depth of stock of the box is held constant by suitablemeans' acting in conjunction with or regulated by air pressure in apressurized closed inlet box, the depth being controlled so that anappreciable amount of stock cannot iiow over the top of the flowdistributor means and the top rectier roll in the stack. On the otherhand, the depth should also be controlled lso that the flow distributormeans and the rectifier roll will be submerged.

The flow distributor means are preferably independently adjustable vanesextending vertically from the floor of the inlet box to just below thecontrolled stock level. The vanes may be arranged accordingly in a flowdistribution chamber at the stock inlet opening, which comprises a ductexpanding laterally from a pipe inlet means to approximately the headbox width at its exit. The vanes positioned in the expanding duct areindependently adjustable so that they may be adjusted to distribute thenecessary amountof stock laterally at different iiow rates in order toeffectively equalize the ow'of stock across the box. Also, it ispreferable that the expanding duct is adapted to receive vertical,preferably upward stock flow from a pipe so that it impinges upon abaille which converts the vertical stock flow to horizontal stock flowdirected toward the vanes.

The rectifier rolls of the stack arespaced apart only su'iciently foroperating clearance and should not provide a flow gap therebetween. Agap of from l; to 1/2 inoh between roll peripheries is satisfactory.Thus, the only restriction to the ow of stock past the vanes through thebox is presented by theprectier roll stack, and this resistance to liowis uniform throughout the entire depth of the stock pond.

The vanes effectively equalize the ow of stock all the way across thebox as it approaches the rectifier roll stack, so that the rectifierroll stack is not subjected to a substantially greater ow of stock atany one given point which might happen to be aligned with the pipe inletmeans from the stock source. In this manner, uniform ilow both laterallyand longitudinally is effected, and the rolling of stock, theoccurrence'of dead spots, and the creation of eddy current is prevented.

The additional rectier rolls at the outlet end of the stock inlet boxare arranged in spaced relation from the outlet opening to form anydesired roll pattern, such as the illustrated arcuate arrangement, whichwill provide a uniform restriction to the flow of stock toward theoutlet. The rolls are grouped so that the stock must flow therethrough,and each of the rolls extends transversely to-the path of stock flow. Byspacing the rectifier rolls of this group from the stock outlet, anyeddy currents generated by the ow of stock through the rolls aredissipated prior to introduction of the stock onto the forming wire, andthe group arrangement of the rolls also prevents the by-passing of stockaround the rolls onto the forming wire.

It is therefore an important object of thepresent invention to providean improved stock inlet for a paper making machine in which uniform flowof stock through the inlet is obtained without the employment of solidbaffles, walls, or the like which are designed to increase appreciablythe travel path of the stock through the inlet box.

Another important object of the present invention is to provide animproved stock inlet for a paper making machine suitably adapted forhigh velocity stock flow through a pressurized closed head box,employing flow distributors or vanes which are directed laterally andangularly with respect to the direction of stock flow in order t"oequalize the stock flow across the head box.

A further object of the present invention is to provide an improvedstock inlet box having a plurality of laterally directed vanescooperating with a plurality of rectifier rolls arranged in spacedrelation from the outlet end of the box in order to effectivelyaccomplish uniform stock flow.

Still another important object of the present invention is to provide animproved stock inlet for paper making machines wherein vane pipe flowdistributors cooperate with bafe means to receive upward flowing stockfrom a pipe, to convert the same to horizontally flowing stock andfinally to uniformly distribute the horizontally flowing stocklaterally.

Other objects, features and advantages of this invention will becomeapparent to one skilled in the art from the following description of theembodiment illustrated in the accompanying drawings.

On the drawings:

Figure l is a top plan view of a stock inlet box embodying theinvention, having the top lid removed; and

Figure 2 is a sectional elevational view, taken substantially along theline ll-II of Figure l, showing parts in whole view and partsdiagrammatically.

As shown on the drawings:

Reference numeral refers generally to a stock inlet box embodying theinvention. The stock inlet box 19 has a horizontal floor 11 and arisingvertically therefrom, on opposite sides thereof, side walls 12 and 13and a front vertical wall 14, slidably engaged on its front outsidesurface with a slice gate 15. The slice gate 15 has an inwardly turnedtop langel which mounts a set screw assembly 17 for adjusting theposition of the beveled slice tip 18 with respect to the beveled forwardtip of the iloor 11.

The relative positions of the forward tip of the floor 11 and thebeveled slice tip 18 determine the size of the box outlet opening and,therefore, the amount of stock which flows out of the inlet box and ontothe forming wire 19 which is trained about the breast roll 20.

As is best shown in Fig. 2, the inlet box 10 has a generally horizontaloor 11 extending longitudinally (in the direction of stock flow) from aninlet opening at the left hand and to an outlet opening at the righthand end.

As shown best in Figure 1 in plan view, the floor 11 of the inlet box1li is generally rectangular in shape from the forward end underneaththe front wall 14 back between the side walls 12 and 13 until the endsof the side walls are reached. Thereafter, the iioor 11 tapers sharply1n the portion designated by the reference numeral 11a, finally forminga curved apex portion. designated by the reference numeral 11b. Thevertically extending back wall of the inlet box 1t) is shaped to conformwith the contour of the floor 11 and, therefore, consists of a curvedcentral portion 21 having one arm 22 extending angularly and forwardlyto join the side wall 12 and another correspondingly shaped arm 23extending angularly and forwardly to join with the side wall 13. u

A top member 24 (shown diagrammatically in Figure 2) completes the stockinlet box 1d. The top member has substantially the same contour as thatof the floor 11 and joins with the vertically extending wall members 12,13, 14, 21, 22 and 23 to form a closed box. The box so formed is adaptedto be pressurized, or to permit the flow of a stock therethrough undercontrolled air pressure. As shown diagrammatically in Figure 2, themeans for effecting air pressure against the stock in the inlet box mayconsist of a compressedv air inlet line 25 having a valve 26 therein forcontrolling: the ow of compressed 4. air into the box 10. The valve 26is, in turn, connected by an air line 27 to a compressed air tank 23wherein compressed air is maintained at a given pressure by means of thecompressed air pump 29.

It will be appreciated that by the use of compressed air alone undergiven flow conditions it will be possible to maintain a given stocklevel in the box. On the other hand, such a procedure is greatlysimplified by the use of compressed air in conjunction with a blow hole3i) suitably positioned, for example, in the side wall 12, at thedesired stock level, designated herein by the reference numeral 31.

In maintaining a stock level 31 by the use of combination air pressureand the hole 30, it can be seen that if the stock level rises above thehole 30 the additional effect of air pressure will tend to force thestock level back down again by increasing the rate of flow of stock ontothe forming wire. On the other hand, if the stock level falls back downto the level of the hole 3i), then the air pressure above the stock pondis instantly released through the hole 3l?.

A pair of spray lines 32 extend transversely from one side wall 13 toand through the other side wall 12 and are connected to a suitable watersource (not shown). The spray lines 32 contain small holes in the bottompe ripheral portion of each and are adapted to send out a fine spray ofwater, so as to effectively wet the inside walls of the stock inlet box10 and thereby prevent the settling out of small stock particles uponthe inside walls during slight fluctations in stock level.

Near the rear apex portion 11b of the tapered door 11 is an opening 33at which is suitably mounted a stock inlet pipe 34. The inlet pipe 34 isconnected to a suitable stock source (not shown) adapted to supply thestock under pressure and thereby to introduce into the inlet box 10 avertical upward flow of stock, as shown by the arrows in Figure 2.

The upwardly owing stock, entering through the pipe 34 and the opening33, impinges against a baffle 35 extending horizontally in spacedrelation with the opening 33. The bale 35 is a generally circularlyshaped, ilat, rigid sheet extending from the curved central portion 21on the back wall and conforming therewith on one side and having aprotecting wall 35 joining and rising vertically from the forwardarcuate edge portion of the baffle 35 not joined to the curved centralportion 21 of the back wall; The baie 35 is preferably positioned sothat it is just below the level 31 and the protecting wall 36 preventsiiow of stock above and behind the bale 35 into what might constitute adead spot in the stock inlet box 10. It will thus be seen that thebatlle 35 converts vertical stock flow to horizontal stock ow in theinlet box 1() and in so doing it diverts the horizontal flow of stockagainst a-plurality of (generally upright) vanes 37.

As shown best in Figure 2, wherein only one vane 37 is shown for thesake of simplicity, the vane 37 is an essentially rectangular verticallyextending sheet of suitable rigid material such as a metal. The vane 37has a sleeve portion 37a positioned near the leading edge 37b. Thesleeve portion 37a receives and ixedly engages a shaft 38 extendingthroughout the sleeve 37a from the top of the vane 37 out to the bottomof the sleeve 37a through an aperture in the floor 11. A hub 39 ismounted on the bottom ofk theshaft 38 below the floor 11. The hub 39,the shaft 38 and the apertured portion of the floor 11 cooperate topermit rotation of the shaft 38 and to form a fluid-tight seal so as toavoid stock leakage. The hub 39 and the shaft 3S are mounted forrotation upon the floor 11 by means (not shown) which are well known inthe art and the axial movement of the shaft 38 is prevented thereby.

Each of the vanes 37 is independently adjustable. An adjusting arm 40extends generally parallel to the door 11 and below the floor 1.1- andis connected to the hub 39 for rotation thereof'. The adjusting arm 40is slotted longitudinally to receive slidably a Wingnut assembly 41'."The bolt portion of the-wing `nut assembly 41is adapted*- to slidablyengagel an arcuate slot or groove 42 cut in the bottom edge of the oor11. It will be appreciated that when the wing nut is loose in the wingnut assembly 41, the actuating arm 40 may be moved to rotate the vane 37and the wing nut assembly will slide freely in the arcuate groove 42 andthe slotted portion of the adjusting arm 40. When the proper positionhasl lbeen reached the wing nut may be tightened and the vane 37 is thenheld in position. l

By the use of the-individually adjustable vanes 37 it is possible tomake adjustment for various ow rates so that proper distributionlaterally of the flowing stock may be obtained in each case. It can alsobe seen that the overall travel path of the stock is not appreciablyaffected by the use of the instant vanes 37. As the stock leaves thevanes 37 it flows uniformly across the inlet box 10, in that the rate offlow at any of the various points on either side section of the inletbox is substantially the same as the rate of flow through the middle ofthe inlet box 10. The rate of flow is thus equalized or uniform at allpoints across the stock inlet box 10 as the stock passes out of theexpanding duct portion defined by the tapered oor portion 11a and thearms 22 and 23 of the back wall.

As the stock departs from the vanes 37 it comes into contact with aplurality of superimposed horizontally aligned rectifier rolls, in thiscase a pair of rolls 43 and 44, rotatably journaled in the opposite sidewalls 12 and 13 of the box 10 and adapted to be rotated by suitablemeans (not shown), as for example by means of individual variable lspeedreversible electric motors.

The stack of superimposed rectifier rolls 43 and 44 presents a uniformrestriction to the flow of stock entering into the full width of the box10.4 It Will be noted that the top roll 43 extends to just below thestock level 31.. The rolls 43 and 44 are spaced apart through the heightof the stacks, the peripheries of the rolls preferably being about 1A to1/2 inch apart. Such a distance is not sufficient to open a flo-w pathbetween the rolls, while the rolls are maintained out of peripheralcontact to prevent the formation of pressure nips therebetween whichmight interfere with the uniform stock flow through the box. Thedirection of drive of the rolls relative to one another is selective tosuit conditions desired and the rolls Vare preferably rotated at verylow speeds with rotation serving merely to clean the holes. The speed ofrotation may be. as low as about 5 to 10 R. P. M., with the holes beingcleaned by the reversed flow through the rolls as they are rotated. Thusa ow through the box is caused by the introduction of stock underpressure into the box 10 and not by any pumping action which might beexerted by the rolls 43 and 44. p

As has been Vmentioned before, it is preferred that the stack of rolls43 and 44 be of such height that the upper roll 43 is substantiallysubmerged within the stockvflowing through the inlet box 10. 'It islikewise preferred that the vertically extending vanes 37 each do notextend above the top peripheralportion of the upper roll 43, and thevanes 37 will likewise be substantially submerged within the -stockflowing through the inlet box 10. It will be appreciated that the extentto which the uppermost roll 43 and the vanes 37 are submerged isexaggerated in Figure V2, for the sake of emphasizingthis preferredfeature of the invention. Actually, the extent to which the rolls or thevanes are submerged is essentially that extent which is necessary toavoid the possibility of stock particles collecting at the top portionsof such members. In addition, the rotation of the rolls 43 and 44 tendsto reduce appreciably any tendency of stock particles to collect on suchmembers. The divergent, probably fluctuating, flow against the leadingedge 37b of the vanes 37 caused by the sharp change of direction of thestock thereat, also tends to reduce appreciably any accumulation ofstock particles upon the leading edge 37b" of each vane.

The individual rolls 43 and 44 are each provided with a plurality ofgraded perforations in a manner well known in the art, such as todiminish in capacity inwardly from the ends of the rolls, the ends ofeach of the rolls being scalloped or perforated with semi-aperturesformed by the intersection of the terminal apertures of the ends of therolls. The aperture arrangement is such that a uniform flow rate alongthe entire length of the roll is maintained, the frictional drag or skineffect on the flow of the flowing stock normally imparted by thestationary side walls 12 and 13 of the box 10 being thus compensated forby the reduced capacity hole of the mid-section of the roll.

It will, of course, be appreciated that the equalizng effect of thevariations in the apertures in the rolls s essentially a nal touch inthe flow control and is not adapted to equalize radically different flowrates across the inlet box. The vanes 37 of the instant apparatus serve'to accomplish the basic equalization of ow, whereas the rolls 43 and 44more or less perfect the uniformity of flow.

Although in the specic embodiment of Figure 2 a stack consisting of tworectifier rolls 43 and 44 has been shown, it will be appreciated thatthe number of rolls in the stack and the relative sizes of the rolls maybe varied in accordance with the level of stock within the chamber.Under some` conditions, it is possible to use only one rectifier rollwith a given height of stock and the number of rolls in the stackgenerally increases in accordance with an increase in desired depth forthe stock pond.

In Figures l and 2 it will also be noted that a plurality of rectierrolls, in this case a pair of rolls'45 and 46, are mounted adjacent thefront wall 14 of the box 10. The rolls 45 and 46 are peripherallyapertured and are substantially identical in construction with the rolls43 and 44. The rolls 45 and 46 are each provided with a separate,variable speed reversible motor (not shown) t0 provide individualcontrol for the direction of speed of rotation of each roll. lt ispreferred that the rolls 45 and 46, which are spaced as hereinbeforeexplained, be driven in opposite directions to ow stock uniformly and ata given rate onto the forming wire 19. The rolls 45 and 46 may be soarranged, as illustrated, so that the portion of the peripheries nearestthe slice tip 1S falls on an arc subtended by a radius having its centergenerally forward of the inlet box and along the forming wire 19.

The rolls 45 and 46 are preferably mounted in a bridging arrangementadjacent the outlet opening so as to control the entire ow of stock fromthe inlet box onto the forming wire 19. It has been found that one rollpositioned adjacent a slice, as heretofore conventionally employed inthe art, sometimes results in the streaking of stock deposited on thewire and the formation of fingers on the wire, or a broom effect in thedeposited stock. By the employment of the plurality of bridging rolls 45and 46, any turbulence which might be introduced in the stock by thepassage through the rolls 45 and 46 may be dissipated prior tointroduction of the stock onto the forming wire 19. i

As in the case of the rolls 43 and 44, it is desirable to have theuppermost rolls 45 substantially submerged below the stock level 31, forthe reasons hereinbefore mentioned.

It will thus be seen that by the combination of the vanes 37 and thestack of rectifying rolls 43 and 44, it is possible to obtainsubstantially uniform stock flow both longitudinally of the direction offlow and transversely of that direction. The baffle 35 and the expandingduct housing the baffle 35 and the vanes 37 are uniquely adapted toeffect the main correction or equalization of the stock flow laterallyand the rectifier rolls 43 and 44 in cooperation therewith accomplishthe final touches in the stock control. j f

This is a continuation-impart of my copending application,SerialrNo.81,951, filed March 17, 1949 and issuedY September 14, 1954 as U. S.Patent No. 2,688,905, and ow'nedfbyy the assignee-of this application.

It will, of course, be understood that various details of constructionmay be varied through a Wide range without departing from the principlesof this invention, and it is, therefore, not the purpose` to limit thepatent granted hereon otherwise than necessitated by the scope of theappended claims.

I claim as my invention:

1. A stock inlet box for a paper'making machine coniprising a head boxhaving a generally horizontal floor extending longitudinally from aninlet opening at one end for receiving stock from a source thereof to anoutlet opening at the other end for flowing stock onto the forniing Wireof the machine, a duct mounted at the head box inlet, said ductexpanding laterally from a pipe inlet opening to a head box size exitfrom which stock ilows into the head box inlet, a horizontally alignedtransversely extending rectifier roll mounted Within the box in spacedrelation from the duct exit to present a uniform restriction to the flowof stock through the box for preventing rolling of stock and theformation of dead stock areas within the box, laterally directed uprightvanes mounted in the duct for equalizing the stock flow across the headbox, and means for maintaining a level of stock in the box that willsubmerge the roll and the vanes.

2. A stock inlet box for a paper making machine cornprising a head boxhaving a generally horizontal floor extending longitudinally from aninlet opening at one end for receiving stock from a source thereof to anoutlet opening at the other end for ilowing stock onto the forming wireof the machine, a duct mounted at the head box inlet, said ductexpanding laterally from a pipe inlet opening to a head box size exitfrom which stock flows into the head box inlet, means llowing stockupwardly through said pipe inlet, a horizontal baille opposing said pipeinlet to convert upward ilow of stock therefrom into horizontal tlow insaid duct, a horizontally aligned transversely extending rectier rollmounted within the box in spaced relation from the duct exit to presenta uniform restriction to the flow of stock through the box forpreventing rolling of stock and the formation of dead stock areas withinthe box, laterally directed upright vanes mounted in the duct forequalizing the stock ilow across the head box, and means for maintaininga level of stock in the box that will submerge the roll and the vanes.

3. A stock inlet box for a paper making machine comprising a head boxhaving a generally horizontal iloor extending longitudinally from aninlet opening at one end for receiving stock from a source thereof andto an outlet opening at the other end for ilowing stock onto the formingwire of the machine, a duct mounted at the head box inlet, said ductexpanding laterally from a pipe inlet opening to a head box size exitfrom which stock flows into the head box inlet, means flowing stockupwardly through said pipe inlet, a horizontal baille opposing said pipeinlet to convert upward ilow of stock therefrom into horizontal ilow insaid duct, a plurality of superimposed horizontally aligned transversely'extending rectifier rolls mounted within the box in spaced relationfrom the duct exit to present a uniform restriction to the llow of stockthrough the box for preventing rolling of stock and the formation ofdead stock areas within the box, laterally directed upright vanesmounted in the duct for equalizing the stock flow across the head box,and means for maintaining a level of stock in the box that will submergethe roll and the vanes.

4. A stock inlet box for a paper making machine comprising a head boxhaving a generally horizontal iloor extending longitudinally from aninlet opening at one end for receiving stock from a source thereof to anoutlet opening at the other end forllowing stock onto the forming wireof the machine, a duct mounted at the head box inlet, said ductexpanding laterally from a pipe inlet opening toa head box size exitlfrom which stock flows into thehead'box inlet, a plurality ofsuperimposedhorizontally aligned transversely extending rectifier rollsmounted within thebox inspaced relation from the duct exit to present auniform restriction to the flow of stock through the box for preventingrolling of stock and the'formation of dead stock areas within the box,laterally directed up right varies mounted in the duct for equalizingthe stock ilow across the head box, and means for maintaining a level ofstock in the box that will submerge the roll and the vanes.

5. A stock inlet box for a paper making machine comprising a head boxhaving a generally horizontal iloor extending longitudinally from aninlet opening at one endfor receiving stock from a source thereof to anoutlet opening at the other end for flowing stock onto the forming wireof the machine, a duct mounted at the head box inlet, said ductexpanding laterally from a pipe inlet opening to a head box size exitfrom which stock flows into the head box inlet, a horizontally alignedtransversely extending rectifier roll mounted within the box in spacedrelation from the duct exit to present a uniform restriction to the flowof stock through the box for preventing rolling of stock and theformation of dead stock areas within the box, laterally directed uprightvanes mounted in the duct for equalizing the stock flow across the headbox, means for maintaining a level of stock in the box that willsubmerge the roll and the vanes, and means for controllably exerting airpressure against the stock in said box.

6. A stock inlet for a paper making machine comprising a closed head boxhaving a generally horizontal lloor extending longitudinally from aninlet opening at one end thereof for receiving stock from a suitablesource to an outlet opening adjacent the other end for flowing stockonto the forming wire of the machine, a duct mounted at the head boxinlet, said duct expanding laterally from a pipe inlet opening to a headbox size exit from which stock iiows into the head box inlet, ahorizontal baille in said duct positioned to convert upward inlet stockflow to horizontal stock ilow, a plurality of upright vanes directlybehind said baille, each of said vanes being independently adjustable todivert stock flow laterally in controllable amounts, a verticallyextending stack of rectifier rolls extending transversely to thehorizontal stock flow behind said vanes, a plurality of horizontallyaligned rectifier rolls mounted adjacent said outlet opening to permitdissipation of turbulence in the stock prior to its exit throughsaidropening, means for controllably exerting air pressure against thestock in the closed head box, and means for maintaining a level of stockin the box that will submerge said rolls and said vanes.

References Cited in the file of this patent UNITED STATES PATENTS1,771,600 Yoder July 29, 1930 1,846,406 Sweeny Feb. 23, 1932 1,909,150Bell-Irving et al May 16, 1933 2,186,761 Malkin Jan. 9, 1940 2,281,293Lang Apr. 28, 1942 2,345,647 Witham Apr. 4, 1944 2,381,286 Hornbostel etal. Aug. 7, 1945 2,396,695 Goodwillie Mar. 19, 1946 2,465,445 GoldsmithMar. 29, 1949 2,509,822 Hornbostel May 30, 1950 2,548,108 HornbostelApr. 10, 1951 2,550,552 Goodwillie Apr. 24, 1951 2,608,912 Davis sept.2, 1952 2,664,033 Hornbostel et al Dec. 29, 1953 2,684,690 Lee July 27,1954 2,688,905 Hornbostel Sept. 14, 1954 FOREIGN PATENTS 254,873 GermanyDec. 17, 1912 359,594 Great Britain Oct. 29, 1931 469,203 Great BritainJuly 21, 1937 478,859 Canada Nov. 27, 1951

